As a renewable energy source bio-hydrogen production from lignocellulosic wastes is a promising approach which can produce clean fuel with no CO2 emissions. Utilization of agro-industrial residues in solid state fermentation (SSF) is offering a solution to solid wastes disposal and providing an economical process of value-added products such as hydrogen. In this study three different particle size of rice husk (<2000 mu m, <300 mu m, <74 mu m) was subjected to batch SSF with a Clostridium termitidis: Clostridium intestinale ratio of 5:1. C. termitidis is a cellulolytic microorganism that has the ability to hydrolyze cellulosic substances and C. intestinale is able to grow on glucose having a potential of enhancing hydrogen production when used in the co-culture. 5 g dw rice husk with 75% humidity was used as substrate in SSF under mesophilic conditions. The highest HF Volume (29.26 mL) and the highest yield (5.9 mL H-2 g(-1) substrate) were obtained with the smallest particle size (<74 mu m). The main metabolites obtained from the fermentation media were acetic, butyric, propionic and lactic acids. The second best production yield (3.99 mL H-2 g(-1) substrate) was obtained with the middle particle size (<300 mu m) rice husk with a HF of 19.71 mL. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.